Security Digest · Vulnerability record
CVE-2025-3757: OpenPubkey Vulnerable to Authentication Bypass
Versions of OpenPubkey library prior to 0.10.0 contained a vulnerability that would allow a specially crafted JWS to bypass signature verification.
CVSS 9.3 Critical EPSS 0.4% · p36
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.4%, percentile 36: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 36% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
github.com/openpubkey/openpubkey(Go) < 0.10.0, fixed in 0.10.0. Check your lockfile, including transitive dependencies.
What it is
Versions of OpenPubkey library prior to 0.10.0 contained a vulnerability that would allow a specially crafted JWS to bypass signature verification.
From the GitHub advisory
Impact
Versions of OpenPubkey library prior to 0.10.0 contained a vulnerability that would allow a specially crafted JWS to bypass signature verification.
Patches
Upgrade to v0.10.0 or greater. This vulnerability is not present in versions of OpenPubkey after v0.9.0.
References
Weakness type: CWE-305.
Product: github.com/openpubkey/openpubkey (Go) · Assigned by: cloudflare · Published: 2025-05-13
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| Go | github.com/openpubkey/openpubkey | < 0.10.0 | 0.10.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| OPKSSH | OPKSSH | Openpubkey <= 0.9.0 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| cloudflare | 4.0 | 9.3 Critical | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L/AU:Y |
| GitHub | 4.0 | 9.3 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Attack requirements: none
- Privileges required: none (no login)
- User interaction: none
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.43% probability of exploitation activity in the next 30 days; percentile 36.
Timeline
- — CVE record last updated
- — CVE record published by cloudflare
- — GitHub-reviewed advisory GHSA-537f-gxgm-3jjq published (critical)
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-537f-gxgm-3jjq github.com
- CVE.org record CVE-2025-3757 cve.org
- NVD entry CVE-2025-3757 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com