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CVE-2026-121623

CVE-2026-121623

validatedZero produced an exploit or a check.

GHSA-pxj9-jh84-vhm5 ↗EUVD-2026-118332 ↗

check availableZero validated a working check for it.not proven exploitableZero has a detection check, but hasn't produced a full working exploit yet.
cve.org+2.2dpublic pocExploit code has been published by someone. Source signals can also carry a PoC (Proof of Concept).kevAttacks confirmed in the real world.
composer:symfony/serializer <5.4.56; >=6; <6.4.50; >=7; <7.4.23; >=8; <8.1.11
fixed in 5.4.56, 6.4.50, 7.4.23, 8.1.11
CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), CWE-73 External Control of File Name or Path
ETK-2026-3494Zero's internal tracking ID, independent of the CVE number., permanent identifier
pkg:composer/symfony/serializer
pkg:composer/symfony/symfony
cvss8.2nvdCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
−2.2dTTV
9mAI analysisAnalysis: how long the AI spent reversing this signal.
Check if you are vulnerable
timeline
0 = cve.org publication
trigger signal −2.2dcheck available−2.2dagent stoppedcve.org publication
−2d
−1d
0

description

Symfony Serializer can interpret specially cased data URIs as local filesystem paths during deserialization. An attacker may read local files when the application deserializes untrusted input into supported file object types, including request-mapped DTO properties in applicable Symfony versions.

mitigation

Upgrade symfony/serializer and symfony/symfony to 5.4.56, 6.4.50, 7.4.23, or 8.1.11, as appropriate for the deployed branch. Until upgraded, avoid deserializing untrusted data into file-related types.

fixed in 5.4.56, 6.4.50, 7.4.23, 8.1.11

check
available
exploit
no
automationDeterministic: a check that runs on its own, the same request on every target. Contextual: an agentic technique that needs to be applied per target, for bugs that depend on contextual flows.
contextual
auth requiredWhether an attacker needs an account first, based on the CVSS vector's Privileges Required.
no
EPSSEstimate of the chance this CVE is exploited in the next 30 days. Refreshed daily.
–
agent run time
9m
cve.org record, t = 0The moment cve.org publishes the CVE in full.
2026-11-06 16:08Z
Δ to public pocExploit code has been published by someone. Source signals can also carry a PoC (Proof of Concept).
–
Δ to kevAttacks confirmed in the real world.
–

outcome

Contextual check: a technique exists and was validated, but no deterministic check could cover this one.

source signals

Public signals that triggered or updated the pipeline. These are inputs for the deltas above.

  1. 2026-11-04 11:43Z
  2. 2026-11-06 16:08Z

this entry in the feed

GET /api/v1/feed/CVE-2026-121623

{
  "etk_id": "ETK-2026-3494",
  "cve_id": "CVE-2026-121623",
  "display_id": "CVE-2026-121623",
  "ghsa_id": "GHSA-pxj9-jh84-vhm5",
  "euvd_id": "EUVD-2026-118332",
  "status": "published",
  "anchor_state": "anchored",
  "title": "Path traversal in Symfony Serializer URI normalization",
  "summary": "Symfony Serializer can interpret specially cased data URIs as local filesystem paths during deserialization. An attacker may read local files when the application deserializes untrusted input into supported file object types, including request-mapped DTO properties in applicable Symfony versions.",
  "mitigation": "Upgrade symfony/serializer and symfony/symfony to 5.4.56, 6.4.50, 7.4.23, or 8.1.11, as appropriate for the deployed branch. Until upgraded, avoid deserializing untrusted data into file-related types.",
  "vendor": "composer",
  "product": "composer:symfony/serializer",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        "<5.4.56"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "5.4.56"
      ],
      "package_name": "symfony/serializer",
      "purl": "pkg:composer/symfony/serializer"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">=6",
        "<6.4.50"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "6.4.50"
      ],
      "package_name": "symfony/serializer",
      "purl": "pkg:composer/symfony/serializer"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">=7",
        "<7.4.23"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "7.4.23"
      ],
      "package_name": "symfony/serializer",
      "purl": "pkg:composer/symfony/serializer"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">=8",
        "<8.1.11"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "8.1.11"
      ],
      "package_name": "symfony/serializer",
      "purl": "pkg:composer/symfony/serializer"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        "<5.4.56"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "5.4.56"
      ],
      "package_name": "symfony/symfony",
      "purl": "pkg:composer/symfony/symfony"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">=6",
        "<6.4.50"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "6.4.50"
      ],
      "package_name": "symfony/symfony",
      "purl": "pkg:composer/symfony/symfony"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">=7",
        "<7.4.23"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "7.4.23"
      ],
      "package_name": "symfony/symfony",
      "purl": "pkg:composer/symfony/symfony"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">=8",
        "<8.1.11"
      ],
      "ecosystem": "composer",
      "fixed_versions": [
        "8.1.11"
      ],
      "package_name": "symfony/symfony",
      "purl": "pkg:composer/symfony/symfony"
    }
  ],
  "cwes": [
    22,
    73
  ],
  "cvss_score": 8.2,
  "cvss_src": "nvd",
  "cvss_vector": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
  "epss_score": null,
  "epss_percentile": null,
  "epss_asof": null,
  "automation": "contextual",
  "check": true,
  "check_confidence_basis": "assessed",
  "exploit": false,
  "pipeline_minutes": 9.245062833333334,
  "t0_at": "2026-11-06T16:08:32.425000+00:00",
  "signals": {
    "check": {
      "at": "2026-11-04T12:15:25.524499+00:00",
      "days": -2.1618854224652777,
      "is_lower_bound": false,
      "measured_at": "2026-11-06T16:08:32.425000+00:00",
      "url": null
    },
    "trigger_signal": {
      "at": "2026-11-04T11:43:37+00:00",
      "days": -2.183974826388889,
      "is_lower_bound": false,
      "measured_at": "2026-11-06T16:08:32.425000+00:00",
      "url": "https://github.com/symfony/symfony/security/advisories/GHSA-pxj9-jh84-vhm5"
    }
  }
}

Anchor corroborated by the cve.org commit 935c5572785b.

published 2026-11-04 12:06Z
last change 2026-11-08 00:40Z

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