major vulnerability· requires attention

Impacts multiple supported Symfony releases; unauthenticated requests can cause widespread DoS of PHP web services using Symfony, a widely used enterprise PHP framework.

Web

CVE-2026-123792

8.7

High

EPSS 0.50%Patch available

Symfony YAML parser flaw enables crafted YAML to exhaust PHP workers and cause DoS.

exploited

No known exploitation not in CISA KEV as of our last sync

fix

Patch available see the advisory in the references

likelihood

EPSS 0.50%top 57% of scored CVEs

Published 6 Nov 2026Analysed here 9 Nov 2026CVSS scored by the publisher (CNA)

common questions

Is CVE-2026-123792 being exploited?

Not confirmed. CVE-2026-123792 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. EPSS currently estimates a 0.50% probability of exploitation in the next 30 days.

How severe is CVE-2026-123792?

CVE-2026-123792 is rated High with a CVSS score of 8.7. 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-2026-123792?

Yes. A fix has been recorded for CVE-2026-123792. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2026-123792 affect?

CVE-2026-123792 affects Symfony < 5.4.56, Symfony 6.x < 6.4.50, Symfony 7.x < 7.4.23, Symfony 8.x < 8.1.11, 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-2026-123792?

Upgrade Symfony to fixed versions ASAP; block or validate YAML content-types and restrict acceptFormat.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

executive summary

technical analysis

affected

Symfony < 5.4.56Symfony 6.x < 6.4.50Symfony 7.x < 7.4.23Symfony 8.x < 8.1.11Any app parsing untrusted YAML with default flags (including MapRequestPayload cases)

impact

Unauthenticated remote request with YAML content causes exponential parsing and memory use, exhausting PHP workers and causing service denial.

action required

Immediate action required

affected versions

sensiolabs symfony

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.

timeline

6 Nov 2026Published
6 Nov 2026CVE record last updated · same day later
9 Nov 2026Analysed by vulneraibility.com · 3 days later

also known as

GHSA-hwfg-qwvh-2wfx

how to fix

Remediation steps are tailored for users whose stack is affected. Add this technology to your stack to see the fix checklist.

references

NVD CVE.org CVE Details Source

4 references in the CVE record: 1 advisory, 3 patches

Advisorygithub.com /symfony/symfony/security/advisories/GHSA-hwfg-qwvh-2wfx
Patchgithub.com /symfony/symfony/commit/487f63bf2cacebc8ed8273c5c10d92955acd2402
Patchgithub.com /symfony/symfony/commit/08db22d52e5d3e6ec2f5c50db30a4d818100ffb9
Patchgithub.com /symfony/symfony/commit/49e03035eda3000e978a4612db74900013255ccd

sources

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
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.

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