Bug 1379302 (CVE-2016-6309) - CVE-2016-6309 openssl: Use After Free for large message sizes
Summary: CVE-2016-6309 openssl: Use After Free for large message sizes
Alias: CVE-2016-6309
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On:
Blocks: 1367347
TreeView+ depends on / blocked
Reported: 2016-09-26 10:33 UTC by Tomas Hoger
Modified: 2021-06-10 11:33 UTC (History)
33 users (show)

Fixed In Version: openssl 1.1.0b
Doc Type: If docs needed, set a value
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Clone Of:
Last Closed: 2016-09-26 10:36:59 UTC

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Red Hat Knowledge Base (Solution) 2662211 0 None None None 2016-09-28 00:42:26 UTC

Description Tomas Hoger 2016-09-26 10:33:03 UTC
Quoting form the OpenSSL upstream advisory:

Fix Use After Free for large message sizes (CVE-2016-6309)

Severity: Critical

This issue only affects OpenSSL 1.1.0a, released on 22nd September 2016.

The patch applied to address CVE-2016-6307 resulted in an issue where if a
message larger than approx 16k is received then the underlying buffer to store
the incoming message is reallocated and moved. Unfortunately a dangling pointer
to the old location is left which results in an attempt to write to the
previously freed location. This is likely to result in a crash, however it
could potentially lead to execution of arbitrary code.

OpenSSL 1.1.0 users should upgrade to 1.1.0b

This issue was reported to OpenSSL on 23rd September 2016 by Robert
Święcki (Google Security Team), and was found using honggfuzz. The fix
was developed by Matt Caswell of the OpenSSL development team.

External References:


Comment 1 Tomas Hoger 2016-09-26 10:36:59 UTC
The CVE-2016-6307 is tracked via bug 1378203.

Upstream commit:


The following commit seems to add test for this issue into upstream test suite:



This issue did not affect any Red Hat product as they do not yet include OpenSSL 1.1.0.

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