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Bug 910553 (CVE-2023-38408) - <net-misc/openssh-9.3_p2: Remote code execution in ssh-agent PKCS#11 support
Summary: <net-misc/openssh-9.3_p2: Remote code execution in ssh-agent PKCS#11 support
Alias: CVE-2023-38408
Product: Gentoo Security
Classification: Unclassified
Component: Vulnerabilities (show other bugs)
Hardware: All Linux
: Normal major (vote)
Assignee: Gentoo Security
Whiteboard: A2 [glsa+]
Depends on: 910555
  Show dependency tree
Reported: 2023-07-19 14:38 UTC by Sam James
Modified: 2023-12-28 03:43 UTC (History)
1 user (show)

See Also:
Package list:
Runtime testing required: ---


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Description Sam James archtester Gentoo Infrastructure gentoo-dev Security 2023-07-19 14:38:25 UTC
Changes since OpenSSH 9.3

This release fixes a security bug.


Fix CVE-2023-38408 - a condition where specific libaries loaded via
ssh-agent(1)'s PKCS#11 support could be abused to achieve remote
code execution via a forwarded agent socket if the following
conditions are met:

* Exploitation requires the presence of specific libraries on
  the victim system.
* Remote exploitation requires that the agent was forwarded
  to an attacker-controlled system.

Exploitation can also be prevented by starting ssh-agent(1) with an
empty PKCS#11/FIDO allowlist (ssh-agent -P '') or by configuring
an allowlist that contains only specific provider libraries.

This vulnerability was discovered and demonstrated to be exploitable
by the Qualys Security Advisory team. 
In addition to removing the main precondition for exploitation,
this release removes the ability for remote ssh-agent(1) clients
to load PKCS#11 modules by default (see below).

Potentially-incompatible changes

 * ssh-agent(8): the agent will now refuse requests to load PKCS#11
   modules issued by remote clients by default. A flag has been added
   to restore the previous behaviour "-Oallow-remote-pkcs11".

   Note that ssh-agent(8) depends on the SSH client to identify
   requests that are remote. The OpenSSH >=8.9 ssh(1) client does
   this, but forwarding access to an agent socket using other tools
   may circumvent this restriction.
Comment 1 Sam James archtester Gentoo Infrastructure gentoo-dev Security 2023-07-19 14:38:36 UTC
I'm doing the bump.
Comment 2 Larry the Git Cow gentoo-dev 2023-07-19 14:41:26 UTC
The bug has been referenced in the following commit(s):

commit 704e9eeeaeb28174462b3a4c68376f43bbfa6765
Author:     Sam James <>
AuthorDate: 2023-07-19 14:41:10 +0000
Commit:     Sam James <>
CommitDate: 2023-07-19 14:41:16 +0000

    net-misc/openssh: add 9.3_p2
    Signed-off-by: Sam James <>

 net-misc/openssh/Manifest              |   2 +
 net-misc/openssh/openssh-9.3_p2.ebuild | 379 +++++++++++++++++++++++++++++++++
 2 files changed, 381 insertions(+)
Comment 3 Larry the Git Cow gentoo-dev 2023-07-20 02:18:31 UTC
The bug has been referenced in the following commit(s):

commit 6394ef8ae23b1cf183b45b603eceea6389a3c371
Author:     GLSAMaker <>
AuthorDate: 2023-07-20 02:17:18 +0000
Commit:     Sam James <>
CommitDate: 2023-07-20 02:18:28 +0000

    [ GLSA 202307-01 ] OpenSSH: Remote Code Execution
    Signed-off-by: GLSAMaker <>
    Signed-off-by: Sam James <>

 glsa-202307-01.xml | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
Comment 4 Larry the Git Cow gentoo-dev 2023-07-30 16:43:40 UTC
The bug has been referenced in the following commit(s):

commit 86ac5c16e3149458710b691e1cad81c50be8d661
Author:     Sam James <>
AuthorDate: 2023-07-30 16:26:38 +0000
Commit:     Sam James <>
CommitDate: 2023-07-30 16:42:29 +0000

    sys-devel/binutils: add various hardening options to 2.41
    Newer Binutils has its several configure arguments we can use:
    * --enable-textrel-check={warning,error}
    * --enable-warn-execstack=yes (*)
    * --enable-warn-rwx-segments=yes (*)
    * --enable-default-execstack=no
    We chuck these in now unconditionally (with some stricter changes for USE=hardened,
    as described below) except for those marked with (*) where we whitelist certain
    arches (amd64/arm64/x86 for now) because the autoconf logic is broken, see (it both needs --enable...=no
    rather than --disable, but it also breaks arches where executable stacks are
    In the past (see 47b8db23ff55dd29992198dfbadda53984a4ab2d, e4b8746852919960969944904c59334cecddfe25
    in binutils-patches.git), we patched Binutils to always warn on textrels
    opt-out on a per-build basis with '--no-warn-shared-textrel'). From >= Binutils 2.35,
    upstream has a '--enable-textrel-check=warning' configure option we use.
    For USE=hardened, our new changes for TEXTRELs are equivalent to `-z text`
    which make TEXTRELs fatal.
    Now, while at it, also make TEXTRELs fatal on musl unconditionally because
    musl doesn't support them and they explode at runtime. Yet another reason
    to get rid of them entirely.
    So, in summary: there's several changes here:
    * Make textrels fatal for USE=hardened (we've warned about them for a while
      on all profiles)
    * Make textrels fatal for musl (they don't work there at all, bug #707660)
    * Disable implicit/automatic executable stacks for USE=hardened (plan to do this
      in general later on)
    * Warn on executable stacks in general
    * Warn on RWX segments in general
    See also
    for more information.
    All of this came to mind again after reading the Qualys writeup for the recent
    OpenSSH bug (bug #910553):
    (Note their use of various gadgets involving these.)
    Signed-off-by: Sam James <>

 sys-devel/binutils/binutils-2.41.ebuild | 43 +++++++++++++++++++++++-------
 sys-devel/binutils/binutils-9999.ebuild | 47 ++++++++++++++++++++++++---------
 2 files changed, 68 insertions(+), 22 deletions(-)
Comment 5 Larry the Git Cow gentoo-dev 2023-12-28 03:43:03 UTC
The bug has been referenced in the following commit(s):

commit ceede2829d93ddc41a45fb1502e537f369fff5c0
Author:     Sam James <>
AuthorDate: 2023-12-28 03:07:11 +0000
Commit:     Sam James <>
CommitDate: 2023-12-28 03:07:11 +0000

    net-misc/openssh: drop 9.3_p1-r1, 9.3_p2
    Signed-off-by: Sam James <>

 net-misc/openssh/Manifest                 |   4 -
 net-misc/openssh/openssh-9.3_p1-r1.ebuild | 380 -----------------------------
 net-misc/openssh/openssh-9.3_p2.ebuild    | 383 ------------------------------
 3 files changed, 767 deletions(-)