Skip to main content
Meet us at Black Hat USA 2026— Las Vegas, August 1–6Book a Meeting
Mallory
Back to vulnerabilities
Unrated

stale proxy password leak in libcurl

IdentifiersCVE-2026-9079CWE-522

CVE-2026-9079 is a medium-severity credential leakage vulnerability in libcurl. When libcurl is instructed to clear proxy authentication credentials, it can fail to actually remove the configured proxy password, leaving stale proxy credentials associated with the handle. Those old credentials may then be reused in subsequent transfers that should neither know nor use them. The issue affects libcurl versions 8.8.0 through 8.20.0 inclusive, does not affect the curl command-line tool, was introduced by commit d5e83eb745762f48d8f, and was fixed by commit 88c7e16cceec816a2df45c89 in curl 8.21.0.

Share:
For your environment

Are you exposed to this one?

Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.

Start free trial
ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause unintended disclosure and reuse of proxy authentication credentials across later libcurl transfers. This can result in a subsequent request being sent with an old proxy password, exposing sensitive credentials to an unintended proxy context and potentially causing authentication to occur with credentials that should have been cleared. The primary impact is credential confidentiality loss and cross-transfer credential leakage rather than direct code execution or memory corruption.

Mitigation

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

If patching cannot be performed immediately, avoid reusing libcurl handles when changing or clearing proxy credentials. Use fresh easy handles for transfers that should not inherit prior proxy authentication state, and review application logic to ensure proxy credential state is not carried across unrelated requests.

Remediation

Patch, then assume compromise.

Upgrade to curl/libcurl 8.21.0 or later, which contains the fix for CVE-2026-9079. If immediate upgrade is not possible, apply the upstream patch corresponding to commit 88c7e16cceec816a2df45c89 and rebuild affected software against the corrected libcurl version.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

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

5 SOURCESView more in app
What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Start free trial
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity1

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

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-9079
NVD
nvd.nist.gov/vuln/detail/CVE-2026-9079
MITRE CWE · CWE-522
cwe.mitre.org