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Mallory
HighPublic exploit

Heap out-of-bounds read in curl secure cookie path comparison

IdentifiersCVE-2025-9086CWE-125· Out-of-bounds Read

CVE-2025-9086 is a vulnerability in curl's cookie handling logic triggered during comparison of cookie paths when a secure cookie previously set for an HTTPS origin is later processed in an HTTP context on the same hostname. According to the provided content, the issue occurs when: (1) a cookie is set with the Secure attribute for an HTTPS target, (2) curl is redirected or otherwise made to communicate with the same hostname over cleartext HTTP while reusing the cookie state, and (3) the same cookie name is set again with path="/" from the insecure context. Due to a bug in the path comparison logic, curl performs a read outside a heap buffer boundary involving memory adjacent to a single-byte allocation holding the path. The vulnerable behavior can either crash the process or cause the comparison to produce an incorrect result, allowing an insecure HTTP response to override a previously established secure cookie, contrary to expected cookie security semantics.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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Successful exploitation can cause a heap out-of-bounds read, resulting in process instability or a crash. More importantly, the faulty comparison may allow a cleartext HTTP site on the same hostname to override the value of a secure cookie that should not be replaceable from an insecure context. This can undermine cookie integrity and security expectations, potentially enabling session manipulation or other application-level impacts depending on how the affected cookie is used.

Mitigation

If you can’t patch tonight, do this now.

No specific temporary mitigation is provided in the supplied advisory content. As a risk-reduction measure, avoid workflows in which curl reuses cookie state across HTTPS and HTTP on the same hostname, especially where redirects or attacker-influenced responses can cause downgrade to cleartext HTTP and set cookies with the same name. Prefer HTTPS-only communication and prevent cleartext access to hosts that rely on secure cookies until patched.

Remediation

Patch, then assume compromise.

Upgrade to a curl release that includes the fix for CVE-2025-9086. The provided advisory content states that affected downstream products, including Apple platforms, addressed the issue through security updates. No more specific patch version is provided in the supplied material.
PUBLIC EXPLOITS

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

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VendorProductType
DebianDebian Linuxoperating_system
HaxxCurlapplication

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ACTIVITY FEED

Recent activity

25 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

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Threat actor evidence

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Social activity24

Community discussion across Reddit, Mastodon, and other social sources.