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CVE Record

CVE-2017-5440: A use-after-free vulnerability during XSLT processing due to a failure to propagate error conditions during...

A use-after-free vulnerability during XSLT processing due to a failure to propagate error conditions during matching while evaluating context, leading to objects being used when they no longer exist. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2017-5440 is a Mozilla memory-safety flaw from 2017. Malformed XSLT processing could make Firefox, Firefox ESR, or Thunderbird use objects after they were freed, causing a potentially exploitable crash. Current risk is mainly in legacy systems still running the affected versions.

Executive priority

Prioritize remediation if any affected versions remain. This is an old client-side vulnerability, so fully patched modern fleets should have low operational urgency, but any legacy browser or mail client handling untrusted content should be treated as a meaningful risk.

Technical view

The flaw is a use-after-free during XSLT matching and context evaluation, caused by failure to propagate error conditions. The affected products are Thunderbird before 52.1, Firefox ESR before 45.9 and 52.1, and Firefox before 53. Sources describe a potentially exploitable crash, but provide no CVSS score here.

Likely exposure

Exposure is likely limited to unsupported or unpatched Mozilla clients: Firefox before 53, Firefox ESR before 45.9 or 52.1, and Thunderbird before 52.1. Enterprise Linux distributions may also be exposed if vendor browser or mail packages from 2017 advisories were never updated.

Exploitation context

The provided sources do not show CISA KEV listing or confirmed active exploitation. The vulnerability is still important because use-after-free bugs in browsers and mail clients can sometimes be turned into code execution, but the bundle only supports “potentially exploitable crash.”

Researcher notes

Evidence is strongest for affected product versions and root cause. The bundle does not provide CVSS, exploit maturity, exploit chain details, or confirmed in-the-wild use. Avoid assuming code execution without additional vendor or threat-intelligence evidence.

Mitigation direction

  • Upgrade Firefox to version 53 or later, or a currently supported release.
  • Upgrade Firefox ESR to 45.9, 52.1, or a currently supported ESR release.
  • Upgrade Thunderbird to 52.1 or a currently supported release.
  • Apply relevant Red Hat or Debian security updates where Mozilla packages are managed by the OS.
  • Check current Mozilla and distribution vendor guidance for any environment-specific instructions.

Validation and detection

  • Inventory installed Firefox, Firefox ESR, and Thunderbird versions across endpoints and servers.
  • Confirm no systems run Firefox below 53 or Thunderbird below 52.1.
  • Check Linux package manager records for the relevant Red Hat or Debian security updates.
  • Review vulnerability scanner findings for CVE-2017-5440 and verify version-based detections.
  • Prioritize validation on systems that process untrusted web pages, email, or attachments.
Prepared
Confidence
high
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2017-5440 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
10Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaThunderbirdunspecifiedListed
MozillaFirefox ESRunspecified, unspecifiedListed
MozillaFirefoxunspecifiedListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.