Answer in brief
CVE-2021-47515 records a High severity (CVSS 7.5) vulnerability in seg6: fix the iif in the IPv6 socket control block. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.0:-:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.0:rc6:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.0:rc7:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.0:rc8:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=c630ec8bdadae9d557b1ceb9d6c06e149108a0d4 <b16d412e5f79734033df04e97d7ea2f50a8e9fe3 || >=2f704348c93ff8119e642dae6a72327f90b82810 <6431e71093f3da586a00c6d931481ffb0dc2db0e || >=ef489749aae508e6f17886775c075f12ff919fb1 <ef8804e47c0a44ae106ead1740408af5ea6c6ee9 || >=ef489749aae508e6f17886775c075f12ff919fb1 <666521b3852d2b2f52d570f9122b1e4b50d96831 || >=ef489749aae508e6f17886775c075f12ff919fb1 <98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1 || >=ef489749aae508e6f17886775c075f12ff919fb1 <ae68d93354e5bf5191ee673982251864ea24dd5c || b71b7e0280f47b4ac633fbfd153423814ea87810 || >=4.14.98 <4.14.258 || >=4.19.20 <4.19.221 || >=4.20.7 <4.21 | b16d412e5f79734033df04e97d7ea2f50a8e9fe3, 6431e71093f3da586a00c6d931481ffb0dc2db0e, ef8804e47c0a44ae106ead1740408af5ea6c6ee9, 666521b3852d2b2f52d570f9122b1e4b50d96831, 98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1, ae68d93354e5bf5191ee673982251864ea24dd5c, 4.14.258, 4.19.221, 4.21 |
| Linux/Linuxgeneric | 5.0 | Not reported |
Published upstream
May 24, 2024
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 4, 2026
In the Linux kernel, the following vulnerability has been resolved: seg6: fix the iif in the IPv6 socket control block When an IPv4 packet is received, the ip_rcv_core(...) sets the receiving interface index into the IPv4 socket control block (v5.16-rc4, net/ipv4/ip_input.c line 510): IPCB(skb)->iif = skb->skb_iif; If that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH header, the seg6_do_srh_encap(...) performs the required encapsulation. In this case, the seg6_do_srh_encap function clears the IPv6 socket control block (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163): memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); The memset(...) was introduced in commit ef489749aae5 ("ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation") a long time ago (2019-01-29). Since the IPv6 socket control block and the IPv4 socket control block share the same memory area (skb->cb), the receiving interface index info is lost (IP6CB(skb)->iif is set to zero). As a side effect, that condition triggers a NULL pointer dereference if commit 0857d6f8c759 ("ipv6: When forwarding count rx stats on the orig netdev") is applied. To fix that issue, we set the IP6CB(skb)->iif with the index of the receiving interface once again.
Quoted source text, attributed separately from HOL analysis.