# CVE-2026-54787: sigstore-go fails to check signature timestamps against a signing key's validity period > Attackers can use expired signing keys to create valid signatures because the library fails to verify timestamps against key validity periods. - **Severity:** Low 3.1 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 31 Jul 2026 - **Updated:** 31 Jul 2026 - **Also known as:** AZL-94425, CLEANSTART-2026-HF60121, DEBIAN-CVE-2026-54787, GHSA-wqqc-jjcq-vfxm, GO-2026-6162, MINI-229j-wj9j-43r5, MINI-27xv-p98c-r2gm, MINI-2v5j-x6v8-rjm8, MINI-2vj2-w2m8-57hx, MINI-36v2-5g7v-m4p4, MINI-3c44-m93v-rjq8, MINI-3mgc-grp3-2mm6, MINI-3r5x-wj8c-7fvx, MINI-3xxg-98q6-hcjc, MINI-423x-mw4h-4mmp, MINI-4rfw-8mq9-r6x8, MINI-4rvh-7hff-575x, MINI-5hhr-w7jr-hq4p, MINI-5rcw-wqwp-h85m, MINI-68mj-57vg-jwh8, MINI-69cc-pjcw-wq5h, MINI-6ggr-wj9f-p9f6, MINI-6gj9-c64h-f5p2, MINI-6phm-j52w-g5ph, MINI-6r2q-fqxj-c8h3, MINI-74x9-3qx8-2qw9, MINI-7874-ffjx-vwrf, MINI-7hm9-p8qp-vqgm, MINI-86gv-hqvr-42hv, MINI-8jm3-5jv3-3qf8, MINI-9583-6hv2-gpfc, MINI-9hhp-rv9g-h5wr, MINI-9q56-m8h5-jrmq, MINI-c2m7-ffh8-phvw, MINI-cf25-f898-x3w9, MINI-cm4w-rcq7-479m, MINI-cpmc-m742-5wv9, MINI-cx33-pfr9-c87m, MINI-f2j7-pmp9-9rjh, MINI-f43x-65j2-76r6, MINI-f68g-82mj-hc9c, MINI-fw5g-r962-hj7q, MINI-g43h-6vpw-qpg3, MINI-g7w5-wx7j-943c, MINI-gwq3-65rg-w73r, MINI-h2cj-87g9-hjfv, MINI-h5x2-7gmw-534j, MINI-hx64-vgv5-7mvp, MINI-j39c-qvrv-fh93, MINI-j8vw-46h6-cmwh, MINI-jjv6-5hcm-ccgj, MINI-m46w-935c-p5cp, MINI-m6rx-9r6x-rw54, MINI-mfxj-ff9h-x8qp, MINI-pfg6-89p6-98wm, MINI-phph-9fmm-7489, MINI-pv2h-jqvm-4wm3, MINI-q42j-7cfq-pq9g, MINI-qh7p-3q3j-8566, MINI-qj92-wfmm-hj6p, MINI-qqjc-vj55-hrv2, MINI-rjvf-5q35-hw3p, MINI-v2wr-3733-qph6, MINI-vg5h-jhxg-98qm, MINI-vvjm-jwjv-x959, MINI-w62p-rcmx-22pc, MINI-w7h9-xvf9-r6mg, MINI-w8hm-682m-66xv, MINI-x388-c72x-m9qq, MINI-x3gf-8j2j-xprv, MINI-x5cm-x6x2-5624, MINI-x7m5-pf9h-35pm, MINI-xg2q-jhrm-4848, MINI-xvpq-v2v3-m5p9, UBUNTU-CVE-2026-54787 ## What is CVE-2026-54787? CVE-2026-54787 is a low-severity vulnerability in sigstore-go, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description sigstore-go is a Go library for Sigstore signing and verification. Prior to 1.2.1, sigstore-go does not check a bundle signing timestamp against the validity window of an ExpiringKey wrapping a self-managed long-lived signing key without a certificate, which can allow an attacker holding expired key material to sign accepted bundles. This issue is fixed in version 1.2.1. Weakness: CWE-324 (Use of a Key Past its Expiration Date) ## Which versions are affected by CVE-2026-54787? 3 open source packages ship an affected version, including github.com/sigstore/sigstore-go. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/sigstore/sigstore-go` | Go | All versions | 1.2.1 | | `github.com/sigstore/sigstore-go` | Go | All versions | 1.2.1 | | `github.com/sigstore/sigstore-go` | Go | All versions | 1.2.1 | ## How do I fix CVE-2026-54787? Upgrade github.com/sigstore/sigstore-go to 1.2.1 or later. ## Is CVE-2026-54787 being exploited? There is no known exploitation of CVE-2026-54787 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-54787 and fix it if it is affected. What it is: CVE-2026-54787 is a low-severity vulnerability in sigstore-go, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-54787 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/sigstore/sigstore-go (Go): affected all versions; fixed in 1.2.1 - github.com/sigstore/sigstore-go (Go): affected all versions; fixed in 1.2.1 - github.com/sigstore/sigstore-go (Go): affected all versions; fixed in 1.2.1 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-54787/ (Markdown: https://insights.sbomify.com/CVE-2026-54787/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54787 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54787 - OSV: https://osv.dev/vulnerability/CVE-2026-54787 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-54787/ Summaries are generated and may contain mistakes; the official description above is the record.