Vancouver, British Columbia--(Newsfile Corp. - September 14, 2026) - Cosa Resources Corp. (TSXV: COSA) (OTCQB: COSAF) (FSE: SSKU) ("Cosa" or the "Company") is pleased to announce results of the summer drilling program at the Company's Murphy Lake North ("MLN") project (Figure 1). MLN is a joint venture (the "Joint Venture") between Cosa and Denison Mines Corp. ("Denison") (TSX: DML) (NYSE American: DNN) and is located three kilometres east of IsoEnergy's Hurricane Deposit. Cosa is the project operator and holds a 70% interest with Denison holding a 30% interest.

Highlights

• Multiple zones of structurally controlled alteration and elevated radioactivity remain open along strike for several hundred meters and on multiple sections

• Drilling evaluated multiple structures over 650 metres of strike length with all 13 drill holes intersecting strong structure and/or alteration

• Summer 2026 drilling prioritized unconformity targets with significant room for basement-hosted mineralization remaining

• With $16 million in the treasury, Cosa remains fully funded for a significant follow up drilling campaign

Keith Bodnarchuk, President and CEO, commented: "We remain very encouraged by the potential at Murphy Lake North. Having previously confirmed the trend hosts uranium mineralization, summer drilling has significantly advanced our understanding of the geology in the immediate area. Highly prospective drill results paired with an abundance of open space emphasize our excitement and commitment to fully evaluating the Cyclone trend and multiple other strong target areas on the Project. With drilling expected to commence at both the Darby joint venture with Denison, and the Aurora project, we expect steady news flow for the remainder of 2026, followed by a return to MLN in early 2027. With $16 million in the treasury and support from our Joint Venture partner and largest shareholder, Denison Mines, the Company is well positioned and fully funded for additional drilling throughout 2027."

Andy Carmichael, VP Exploration, commented: "Drilling at Cyclone has confirmed that the mineralization intersected during the winter drill program is contained within a much larger zone of structure and alteration than previously recognized that remains open for at least several hundred meters along strike in both directions. Drill holes testing unconformity targets over a 650-metre strike length intersected structure and/or alteration in all drill holes, with several targets that remain to be tested in the immediate area. In addition to commencement of drilling at the Darby project in the coming days, we have already begun work on planning an extensive follow up campaign at Murphy Lake North."

Summer Drilling Results

The 13-hole, 6,752 metre drill program followed up winter results at the Cyclone trend highlighted by 5.0 metres averaging 0.55% U₃O₈ (308.5-313.5 metres) in MLN26-013 including a 0.5 metre subinterval of 1.70% U₃O₈ (310.5-311.0 metres). Summer drilling targeted the Cyclone trend over a 650-metre strike length extending 400 metres west and 250 metres east of MLN26-013 (Figure 3). All 13 summer drill holes intersected moderate to strong alteration and/or structure, and several drill holes intersected intervals of elevated radioactivity (Table 1, Figure 3).

Drilling identified two prominent faults, the N- and S-faults, which are generally located along the northern and southern edges of the Cyclone graphitic basement unit. The N-fault is the most prominent basement structure intersected on the project and hosts the zone of strong basement alteration intersected by winter 2026 drill hole MLN26-017.

Drill holes MLN26-023, -024, -25A, -026, and -028 targeted the N-fault at the unconformity and intersected moderate to strong alteration and faulting in the sandstone and/or basement including intervals of hydrothermal hematite. Most of these drill holes also intersected alteration and faulting above the interpreted location of the S-fault. Pending assay results will guide further exploration. The N-fault remains untested at the unconformity west of MLN26-028 and east of MLN26-025 (Figure 3).

Drill holes MLN26-019 and -027 targeted the S-fault at the unconformity. Both holes undershot the target and intersected the fault in the basement. The S-fault remains untested at the unconformity and is interpreted to join the N-fault west of the 2026 drilling area (Figure 3).

Drill hole MLN26-020C1 targeted the zone of strong basement alteration intersected by MLN26-017. Assay results received after the start of summer drilling indicate the zone is strongly enriched in uranium pathfinder elements including Ni and Co, similar to the MLN26-013 mineralization. MLN26-020C1 extended the basement alteration zone 36 m to the east and intersected enrichment of a similar suite of pathfinder elements. This zone remains open down dip and down plunge of MLN26-017.

Next Steps

With C$16 million the treasury, the Company remains well-funded for a significant follow up winter campaign at Murphy Lake North. Immediate follow up targets include the uranium pathfinder element enriched basement alteration zone intersected by MLN26-017 and MLN26-020C1, the S-fault, and the strike extensions of the N-fault. Additionally, the Company expects to announce commencement of drilling at the Darby and Aurora projects in the coming days.

Table 1 – MLN Summer 2026 Radioactive Intersections

About Murphy Lake North

MLN covers a portion of the Larocque Lake trend and is located 3 kilometres east of the Hurricane deposit (Figures 1 and 2). Hurricane is the world's highest-grade indicated uranium resource and was discovered and delineated for IsoEnergy Ltd. by current members of Cosa's team. The Larocque Lake trend also hosts the high-grade Larocque Lake Zone, Yelka Prospect, and Alligator Lake Zone. MLN contains the along-strike extension of basement geology underlying the Hurricane deposit (the Hurricane trend), as well as a parallel conductive trend to the south (the Cyclone trend). Cosa's winter 2026 drill program intersected several metres of basement hosted uranium mineralization within a broader zone of strong structure and alteration at the Cyclone trend.

Figure 1 – Cosa's Eastern Athabasca Uranium Projects

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Figure 2 – Murphy Lake North Project Overview

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Figure 3 – Cyclone 2026 Drilling Area Plan View

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About Cosa Resources Corp.

Cosa Resources is a Canadian uranium exploration company operating in northern Saskatchewan. The portfolio comprises roughly 237,000 ha across multiple underexplored 100% owned and Cosa-operated joint venture projects in the Athabasca Basin region, the majority of which reside within or adjacent to established uranium corridors.

In 2025, the Company entered a transformative strategic collaboration with Denison (TSX: DML) (NYSE American: DNN) that has secured access to several additional highly prospective eastern Athabasca uranium exploration projects. As Cosa's largest shareholder, Denison gains exposure to Cosa's potential for exploration success and its pipeline of uranium projects.

Cosa's award-winning management team has a track record of success in Saskatchewan. In 2022, members of the Cosa team were awarded the AME Colin Spence Award for the discovery of the Hurricane uranium deposit. Cosa personnel led teams or had integral roles in the discovery of Denison's Gryphon deposit and held key roles in the founding of both NexGen and IsoEnergy.

Technical Disclosure

Historical drilling and geophysical results for MLN were sourced from the Saskatchewan Mineral Assessment Database (SMAD). SMAD sources for MLN and adjacent projects include file numbers 64L05-0161, 64L05-0180, 74I-0060, 74I-0066, 74I-0067, 74I01-0114, 74I08-0056, 74I09-0053, 74I09-0057, 74I09-0061, 74I09-0064, 74I09-0066, 74I09-0071, 74I09-0077, 74I09-0079, 74I09-0087, 74I09-0088, 74I09-0090, 74I09-0091, 74I09-0092, 74I09-0098, MAW00510, MAW01939, MAW02327, MAW02599, and MAW02395. Data and reports related to the 2020 ground EM survey completed by Denison are not presently available via SMAD and were supplied to Cosa by Denison.

Verification of historical drilling results included confirming historical drill hole collar locations from air photos and ground checking selected collars with a handheld GPS unit. Basement and lower sandstone sections from most historical drill holes were relogged in 2024 and 2025 by Cosa.

Verification of historical geophysical results included confirming the locations of geophysical survey grids from air photos, compiling survey data and interpretations, and evaluating whether interpreted geophysical results could be reasonably explained by historical and current drilling results. For MLN, Cosa engaged a consultant to re-interpret historical geophysical surveys to validate selected previous interpretations.

Anomalous radioactivity in drill core was measured by removing intervals of drill core to an area of background radioactivity and scanning it with an RS-125 handheld spectrometer to determine average CPS. Sampling of mineralized zones was completed by collecting half-core splits with intervals that align with radioactive measurement intervals. Samples were transported to SRC Geoanalytical Laboratories (SRC) in Saskatoon, Saskatchewan (ISO/IEC 17025:2005 accredited) for U₃O₈ assay and multielement analysis. Cosa inserts certified reference material (CRM) blanks and standards into the split core sample series as a QA/QC measure. SRC conducts a QA/QC programme which includes repeat analyses and insertion of CRM standards CAR218, BL4A, and BL2A. SRC's CRM results are verified by Cosa staff. U₃O₈ assay results are compared to RS-125 handheld scintillometer readings and downhole gamma probe results to verify chemical assays and measured radioactivity align.

Qualified Person

The Company's disclosure of technical or scientific information in this press release has been reviewed and approved by Andy Carmichael, P.Geo., Vice President, Exploration for Cosa. Mr. Carmichael is a Qualified Person as defined under the terms of National Instrument 43-101. This news release refers to neighbouring properties in which the Company has no interest. Mineralization on those neighbouring properties does not necessarily indicate mineralization on the Company's properties.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Cautionary Statements

This press release contains forward-looking information within the meaning of Canadian securities laws (collectively "forward-looking statements"). Forward-looking statements are typically identified by words such as: believe, expect, anticipate, intend, estimate, plans, postulate and similar expressions, or are those, which, by their nature, refer to future events. All statements that are not statements of historical fact are forward-looking statements. These forward-looking statements or information may relate to anticipated exploration, development and/or expansion activities, including exploration of the Company's current Projects; the collaboration with Denison, including the Joint Venture, and the anticipated benefits thereof; and the outlook regarding Cosa's business plans and objectives.

Such forward-looking information and statements are based on numerous assumptions, including among others, that the results of planned exploration activities are as anticipated, the cost of planned exploration activities are as anticipated, that general business and economic conditions will not change in a material adverse manner, that financing will be available if and when needed and on reasonable terms, that third party contractors, equipment and supplies and governmental and other approvals required to conduct Cosa's planned exploration activities will be available on reasonable terms and in a timely manner. Although the assumptions made by Cosa in providing forward-looking information or making forward-looking statements are considered reasonable by management at the time, there can be no assurance that such assumptions will prove to be accurate.

By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors and risks include, among others: Cosa may require additional financing from time to time in order to continue its operations which may not be available when needed or on acceptable terms and conditions acceptable; Cosa may not be able to maintain compliance with its contractual obligations with third parties; Cosa may not be able to maintain compliance with extensive government regulation applicable to its operations; domestic and foreign laws and regulations could adversely affect Cosa's business and results of operations; the stock markets have experienced volatility that often has been unrelated to the performance of companies and these fluctuations may adversely affect the price of Cosa's securities, regardless of its operating performance; the ongoing military conflict in Ukraine, and other risk factors set out in Cosa's public disclosure documents.

The forward-looking information contained in this news release represents the expectations of Cosa as of the date of this news release and, accordingly, is subject to change after such date. Readers should not place undue importance on forward-looking information and should not rely upon this information as of any other date. Cosa does not undertake any obligation to update these forward-looking statements in the event that management's beliefs, estimates or opinions, or other factors, should change.

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Source: Cosa Resources Corp.