Symfony is a widely used PHP framework; this bug can leak default-scope credentials to attacker-controlled origins, impacting many web apps and risking widespread credential theft.
CVE-2026-121971
Symfony HttpClient bug leaks default-scope credentials to attacker-controlled origins.
Is CVE-2026-121971 being exploited?
Not confirmed. CVE-2026-121971 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked.
How severe is CVE-2026-121971?
CVE-2026-121971 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-121971?
Yes. A fix has been recorded for CVE-2026-121971. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-121971 affect?
CVE-2026-121971 affects Symfony HttpClient ScopingHttpClient, Symfony 5.x < 5.4.56, Symfony 6.x < 6.4.50, Symfony 7.x < 7.4.23, and 1 further product or version. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-121971?
Upgrade to fixed Symfony versions, rotate any potentially exposed credentials, and avoid untrusted relative URLs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Credential disclosure: auth_bearer/auth_basic merged into requests resolved to network-path refs (//host) can send creds to attacker-controlled origins.
Immediate action required
- affected< 5.4.56
- affected>= 6.0.0 and < 6.4.50
- affected>= 7.0.0 and < 7.4.23
- affected>= 8.0.0 and < 8.1.11
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
cisa ssvc
- exploitation
- none
- automatable
- no
- technical impact
- partial
Assessed by CISA 4 Nov 2026 (SSVC 2.0.3).
timeline
- 4 Nov 2026Published
- 4 Nov 2026CISA SSVC assessment: exploitation none · same day later
- 5 Nov 2026CVE record last updated · 1 day later
- 7 Nov 2026Analysed by vulneraibility.com · 2 days later
also known as
- Advisorygithub.com /symfony/symfony/security/advisories/GHSA-gq53-v8w2-gjhj
- Patchgithub.com /symfony/symfony/commit/64c34e85bd03b3f8a735d8e1af393659dda91d7c
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- OSV: advisory aliases and downstream package versions
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.